The present invention relates generally to hearing test devices and more specifically to an infant hearing screener which uses distortion-product otacoustic emissions (DPOAE) to determine the function of the outer hair cells, which is an indication of middle-ear function. For example, the absence of DPOAE indicates a possible hearing loss.
The otacoustic emissions produced by a healthy ear are extremely small in magnitude. The emissions typically range from -10 db SPL to +20 db SPL. Any kind of extraneous noise introduced into the ear canal or measurement system can mask these emissions and give a false negative response. The microphone must have a very low internal noise level to discriminate the emissions from the system noise. All existing equipment for testing for DPOAE uses a probe which seals into the ear canal and is attached to the measurement equipment through a cable. This type of system is not practical in an infant screener for several reasons.
These reasons include the fact that an infant's ear canal is very small, and as a result, it can be quite difficult to seal a probe into such a small canal any pull on the probe from the attached cable can break the seal or pull the probe out of the canal. In addition, the time required to place a probe in the infant's ear canal significantly slows down the testing process. Typically, the infant is asleep when the testing is performed so that movement is minimal. The process of putting the probe into the infant's ear canal in a manner so that it stays for the duration of the test often wakes the infant which, of course makes the test difficult or impossible to perform.
While a hand-held screening device alleviates many of the above discussed problems, implementation of such a device has inherent problems which must be overcome to provide an effective hearing measurement device. One such problem results from the vibrational noise generated by the tester's hand during the testing. This noise is transmitted through the device and into the microphone which prevents accurate measurements. Holding a conventional probe to the ear canal creates a noise level that completely masks any emissions that could otherwise be detected.
Another problem is the difficulty in achieving a consistent seal to the infant's ear canal. Difficulty in maintaining the seal results from minor movements of the infant's head and/or the tester's hand. An embodiment of the screener solves the above problems, thereby providing a screener for performing DPOAE testing quickly and easily.